This invention relates to an improved fluid T-coupling filter system. A fluid T-coupling typically has first and second fluid flow channels which are generally perpendicular to, and in communication with, one another. The second fluid flow channel opens into a side of the first fluid flow channel so as to form a "T".
One particular use of the T-coupling filter system of this invention is with a PHACO-EMULSIFIER aspirator during eye surgery. The aspirator is used to remove waste and body fluids from a cavity in the eye. Because of the extremely small volume of this cavity and the fragile nature of the eye tissue, it is critical that enough pressure be present within the cavity to keep it inflated so that the opposing surfaces within the cavity do not rub against one another. It is also critical that high levels of pressure be avoided within the cavity as this could cause the cavity to rupture, resulting in severe tissue damage.
The PHACO-EMULSIFIER aspirator is typically utilized in conjunction with a surgical irrigation/aspiration handpiece. The irrigation channel of the irrigation/aspiration handpiece is connected to a pressurized source of irrigation solution by means of disposable surgical tubing. Before the irrigation/aspiration handpiece is connected to pressurized irrigation reservoir, the connecting tubing is threaded through an irrigation valve on the PHACO-EMULSIFIER aspirator. The valve selectively applies or release pressure on the exterior of the surgical tubing in order to control the flow of the irrigation solution from the irrigation reservoir to the irrigation/aspiration handpiece.
The aspiration channel of the irrigation/aspiration handpiece is connected to a drainage reservoir by means of disposable surgical tubing. A vacuum within the aspiration line is created by means of vacuum pump roller assembly. Before the irrigation/aspiration handpiece is connected to the drainage reservoir the connecting surgical tubing is threaded through a vacuum pump roller assembly. The vacuum pump consists of plural radially extending arms with small rollers at their outer edges. As the arms rotate about a central axis, the rollers pinch the surgical tubing against the flat outer wall of the vacuum pump roller assembly in create a suction at the handpiece tip.
If the inlet of the aspiration channel occludes, the vacuum pump roller assembly could theoretically create an unlimited level of vacuum within the tubing. In order to avoid this dangerous situation, a fluid T-coupling is used to connect the surgical tubing connected to the irrigation/aspiration handpiece to the surgical tubing which is threaded through the vacuum pump roller assembly. The first flow channel of the T-coupling is coincident with the aspiration channel and permits body fluids to flow from the surgical site to the drainage reservoir. The second flow channel, commonly called the vacuum vent, is connected to the vacuum vent of the PHACO-EMULSIFIER aspirator which releases the vacuum when predetermined suction or vacuum level is reached.
The irrigation/aspiration handpiece is typically controlled by means of a foot pedal. When the pedal is depressed, the vacuum pump rollers rotate, thereby creating suction at the handpiece tip. When the pedal is released, the rollers stop. However, during the aspiration process, the vacuum created within the surgical tubing connecting the pump and the handpiece causes the tubing to constrict along its entire length. When the rollers stop, the natural tendency of the resilient surgical tubing is to spring back to its original diameter. This creates a momentary residual source of vacuum at the handpiece tip. As it is often critical that the vacuum at the handpiece tip be ceased immediately in order to prevent the delicate eye tissue from being damaged, the foot pedal is connected to a solenoid and a delay timer which open the vacuum vent of the PHACO-EMULSIFIER aspirator for one quarter of a second in order to release this residual vacuum yet prevent the aspirated waste fluids from flowing back through the tubing and contaminating the eye cavity.
It is critical that the aspiration channel of the T-coupling is not blocked by the tissue fragments or coagulating blood, otherwise the resulting improper level of vacuum at the surgical site could cause body tissue damage. It is also necessary that the vent path be kept free of blockage as this could cause the level of vacuum communicated to the surgical site to exceed safe levels. Furthermore, it is critical that the connection of the fluid T-coupling to the vent path is consistently accurate, since any misalignment between the fluid T-coupling in the vent path will result in a change in the vacuum level of the system and therefore create the risk of damaging the eye tissue.
A disposable fluid T-coupling presently being used with such a PHACO-EMULSIFIER aspirator is described in U.S. Pat. No. 4,418,944. This fluid T-coupling has a nozzle shaped body with a protruding tab. One of the connecting tubes fits coaxially over one end of the nozzle body and the other fits coaxially into the other end of the nozzle body. This body is then inserted into a mating receptacle in the PHACO-EMULSIFIER aspirator and is rotated about an axis parallel to the axis of the nozzle body and therefore the connecting tubes. The protruding tab serves to linearly align the fluid T-coupling properly within the receptacle. Cam surfaces on the body of the fluid T-coupling and on the surface of the receptacle cooperate to press the vent opening on the fluid T-coupling against the vent opening in the surface of the receptacle in order to provide a seal.
There are concerns, however, which are not provided for at all by the T-couplings presently available. It is critical that bacteria and minute particles entrained in the air entering through the vent path do not cause the contamination of the transmitted body fluids or the surgical site. Furthermore, if tissue or coagulated blood becomes lodged in the vent path it could cause the body fluids to be aspirated at an improper rate. The presence of tissue or coagulated blood in the vent path could also cause contamination. Such contamination occurs when the trapped material decomposes or breeds harmful organisms which subsequently contaminate the transmitted body fluid or the surgical site.
Although the use of disposable fluid T-couplings helps reduce the likelihood of such contamination, it does not eliminate the threat. The vent path can still be contaminated by coming in contact with a contaminated area of the non-disposable portion of the vent path. Contamination is also possible as a result of contact with the atmosphere through the opening of the disposable portion of the vent path during the replacement of the disposable fluid T-coupling.
In an attempt to prevent contamination from the vented air, filters are often inserted on the vent line and connected to the fluid T-coupling by flexible tubing. The use of these filters, and their corresponding filter lines, often leads to a confusing array of interconnecting tubes which easily become entangled and can be unreasonably difficult to connect. A simple reliable fluid T-coupling which assures its proper alignment and prevents contamination is therefore needed.